Twisting head for two-fold yarn



Aug. 23, 1960 G. RENZINI 2,949,725

. TWISTING HEAD FOR TWO-FOLD YARN Filed June 4, 1958 TWISTING HEAD FOR TWO-FOLD YARN Goifredo Renzini, Pizzighettone, Italy, assignor to Pirelli Societa per Azioni, Milan, Italy Filed June 4, 1958, Ser. No. 739,701

Claims priority, application Italy June 6, 1957 7 Claims. (Cl. 57-'58.3"6)

It is known that simultaneous twisting of two-fold yarn for forming the twisted yarn from parallel threads by one step is based on the false twist principle.

The process can be synthetised as follows:

(a) The threads having travelled through false twist devices join at the region where they are twisted together;

(b) The single threads are freely unwound, drawing-01f being mechanically effected on the final twisted yarn;

() One thread is looped about the bobbin from which the other thread extends, the bobbins being placed on a common stator.

Doubling of the two threads at the twisting region can be alternatively effected with a:

(a') Freely rotatable twisting point, (17) Stationary twisting point.

Condition (a) is met by applying to the two single threads forming the twisted yarn tensions which are strictly equal and constant on doubling.

Condition (12') is met by employing a suitable twisting head which should rotate synchronously with the spindle and provide strictly equal rates of feed of the single threads as the latter join for twisting.

The twisting head can be rotated by the outer thread, or individual motors or non-slip belts driven by the driving member rotating the spindle can be employed.

The simplest procedure is to rotate the twisting head from the outer thread forming the balloon.

This invention provides a twisting head of the type referred to above in paragraph (b') which is rotated by the balloon, and is based on the following principles:

(1) False twist of the single threads;

(II) Free unwinding-off of the threads and mechanically operated drawing-off of the twisted yarn;

(III) Driving the head by the thread on the outer bobbin effecting at the same time the false twist of the thread from the inner bobbin; balancing of the tensions on both threads and uniform feeding of the two pre-stressed threads by drawing-off of the twisted yarn.

The improved twisting head affords the following chief advantages over known twisting heads based on the above mentioned principles.

(1) No substantial modification of the existing spindles or two-ply twisting frames is required. The invention implies the use of attachments which can be attached and removed at will.

Consequently, one and the same twisting frame can be employed at will for simultaneous twisting or conventional two-ply twist according to requirements.

(2) The head can be rotated without using thread guides for either the outer or inner thread, which results in improved propertiem of the twisted yarn.

(3) Two distinct and concordant torques as explained hereafter are set up, which are both powerful, thereby affording easy and safe starting of the spindle even with threads of very small gauge.

atent (4) The tensions on the threads are satisfactorily balanced.

(5 Smooth twisted yarns are obtained without employing thread braking means of high accuracy.

(6) Threading of the threads is highly simplified through the absence of thread guides.

(7) The twisting head is of low weight and high strength, which results in high safety against accidents to attendants and improved life.

(8) The twisting head is inexpensive through its simplicity in construction.

The invention shall be described in detail hereafter with reference to the accompanying drawing which shows an embodiment by way of a non-limiting example.

Figure 1 is a part sectional front view of the twisting head,

Figure 2 is a part sectional View on line IIII of Figure 1, and

Figure 3 is a schematic view of the plant including the improved twisting head. i

The twisting head comprises a U-shaped support 1 having two parallel branches 2, 3 differing in length.

The head is assembled with the branches extending parallel with the plane of the spindle rotor, the shorter branch 2 lying above the longer branch 3.

The shorter branch 2 has a conical hole bored at 4 to receive a steel pivot 5 coaxial with the spindle, the pivot being axially bored and supported by a suitable hearing such as a double ball-row bearing secured by means of its bearing holder 7 on a bar 8 which in conventional twisting frames would carry the thread guides leading the twisted yarn to the drawing-off device, said bar replacing the thread guide in the instant construction.

The support 1 has secured thereto a shaft 11 perpendicular to the axis AA of the pivot 5 but offset from said axis as indicated by a on the drawing. The shaft 11 has keyed thereto pulleys 9, 10 having a groove 12, the groove generatrix (Figure 2) being an asymmetric curve, the minimum radius of which matching the groove depth is situated in a plane near the inner edge of the pulley. This radius substantially matches the eccentricity a of the shaft 11 with respect to the plane parallel with the said shaft extending through the axis AA of the pivot 5.

The groove bottom in the pulleys 9, 10 is therefore tangential to the said plane.

In addition to balancing the unit revolving about the axis of the pivot 5 the longer branch 3 of the support 1 spaces the two threads, namely the thread from the inner spool and the thread from the outer spool forming the balloon which are looped in the manner described hereafter in the pulley grooves and causes the threads to constantly reach the same position in the groove in order to avoid straddling of the thread loops on the pulleys. Moreover the longer branch 3' improves rotation of the twisting head by the balloon forming thread bearing on said branch eccentrically with respect to the rotational axis A-A.

The support 1, 2, 3 and pulleys 9, 10 are all made of superpolyamide (conveniently superpolyamide 6) or other synthetic material of low specific weight having high strength properties.

By the use of the above materials the weight of the twisting head inclusive of all its attachments is about 35-40 grams.

The twisting head operates as follows:

The thread 15 from the outer bobbin 14 having travelled through a suitable brake such as a self-stretching brake having conical grooves, diagrammatically denoted by 16, and axial bore in the spindle 17 and having formed the balloon 15' is looped twice or more on the pulley 9 which it leaves as it is held in the plane parallel with on the branch 3 spacing the threads 15, 19 and loops on the pulley in just the same manner as the outer thread on the pulley 9 and leaves the pulley 10 in the same manner as the thread 15 as it is held in the same plane mentioned above in a symmetrical direction towards the region X where the thread 19 joins in a triangle arrangement the thread 15 with which it travels along the axis of the pivot 5 through the axial bore 6 in the latter to form the twisted yarn.

Obviously, the single threads 15 and 19 are thereby pre-stressed and are held in this condition as they are carried along by the pulleys about which they are looped till they join and form the twisted yarn by involution.

Unwinding of the threads in a pre-stressed condition is effected solely by the twisted yarn which moves the two pulleys solidly rotating with each other and they have Wound thereon a plurality of turns, such as two or three thread loops prevent any slipping of the two single threads adapted to form the twisted yarn.

It will be obvious that though the tensions of the two threads past the pulleys may not be fully equal or constant, provided they are both high enough to prevent slipping of the threads in the pulley grooves, the twisted yarn incorporates accurately equal thread lengths.

What I claim is:

1. In a twisting head a rotatable axially bored pivot positioned on a generally vertical axis, support means fixed on the low end section of the pivot thereby to rotate therewith about the said axis, a cross shaft rotatable in the support means in a plane off-set with respect to the said axis, a pair of grooved pulleys respectively keyed on opposite ends of the cross shaft in planes parallel and symmetrical to the said axis, means for supplying a thread to one of the pulleys, means for supplying a second thread to the other pulley, and means for drawing-off the two threads in doubled and twisted condition through the bore in the pivot.

2. In the twisting head as claimed in claim 1, wherein the groove bottom on each pulley is tangential to the plane extending through the said axis parallel with the said cross shaft.

3. In the twisting head as claimed in claim 1, the support. means comprising a U-shaped member including a bridge portion and a pair of parallel branches, one of the branches being fixed on the low end portion of the pivot perpendicular to the said axis whereby the bridge portion is oft-set and parallel to the axis, the said crossshaft being rotatably supported in the bridge portion.

4. In the twisting head as claimed in claim 3, the other branch being longer than the said one of the branches thereby providing a spacing member for the threads and balancing the head with respect to the said axis.

5. In the twisting head as claimed in claim 3, wherein the U-shaped member and pulleys are made of a superpolyamide.

6. In a twisting head a rotatable axially bored pivot positioned on a generally vertical axis, support means fixed on the low end section of the pivot thereby to rotate therewith about the said axis, a cross shaft rotatable in the support means in a plane oft-set with respect to said axis, a pair of grooved pulleys respectively keyed on opposite ends of the cross shaft in planes parallel and symmetrical to said axis, means for supplying a thread to one of the pulleys, means for supplying a second thread to the other pulley, and means for drawingolf the two threads in doubled and twisted condition through the bore in the pivot, and support means fixed on the upper end section of the pivot for connecting it to atwisting frame.

7. In a twisting head a rotatable axially bored pivot positioned on a generally vertical axis, sup-port means fixed on the,=low end section of the pivot thereby to rotate therewith about the said axis, a cross shaft rotatable in the support means in a plane off-set with respect to said axis, a pair of grooved pulleys respectively keyed on opposite ends of the cross shaft in planes parallel and symmetrical to said axis, means for supplying a thread to one of the pulleys, means for supplying a second thread to the other pulley, and means for drawing-oil the two threads in doubled and twisted condition through the bore in the pivot, a bar provided with a through opening, a bearing surrounding the upper end section of the pivot, and a bearing holder surrounding said bearing and inserted in said opening in said bar, the latter being adapted to be connected to a twisting irame.

References Cited in the file of this patent UNITED STATES PATENTS 

